1. Field of the Invention
The present invention relates to a recognition technology, particularly to a speech recognition device and a speech recognition method.
2. Description of the Related Art
Keyword detection or spotting plays an important role in speech recognition technologies. The speech recognition process includes obtaining the eigenparameters of speech, constructing models for the speech characteristics, and establishing a comparison method for the eigenparameters (calculating distance or similarity). Speech recognition technologies have developed for many years, and a large-scale vocabulary database has been able to achieve a not-bad recognition rate. However, the existing speech recognition technologies are hard to maintain a given level of recognition rate when the environment is contaminated by noise or competing speeches, even for a single keyword. In fact, noise is inevitable for a practical environment.
In the existing ASR (Automatic Speech Recognition) system, determining when to start automatic speech recognition is an important function, which is usually called a wake-up function or a push button. Appropriately using the wake-up function can greatly reduce the error rate of recognition. In a computer or mobile phone, the wake-up function is normally realized via a touch-control operation or a push button. However, such an implementation needs a premise that the hand of the user can reach the device or machine. If the device is not beside the user, the user normally wears a wireless device to generate a reliable wake-up signal. For example, the user has to wear a wireless device to instruct a household robot. However, it is difficult for the user is hard to always wear a wireless device at his home. Therefore, such a measure has barriers in many applications. Thus, how to realize a wake-up function without wearing any device has become a practical and challenging subject. When the controller interface of a controlled device is out of vision, the wake-up function can only be realized via speech. It seems to be a simple problem of recognizing a single keyword. However, the speaker may be remote from the receiver device, or the environment is noisy. In fact, SNR (Signal-to-Noise Ratio) is normally very poor in practical applications. Similar to the push button or touch control, the speech-based wake-up function should also possess almost 100% detection rate and almost 0% false positive rate lest the controlled device act wrong or slowly.
Accordingly, the present invention proposes a speech recognition device and a speech recognition method to solve the conventional problems.